Continuous sandblast apparatus



Jan 29, 1963 s. H. BLUBAUGH 3,075,319

CONTINUOUS SANDBLAST APPARATUS la i l uml /0 60 46 Inl' /30 f 36 0 54 az l 26 INVENTOR.

ATTOKNE YS Jan. y29, 1963 s. H. BLUBAUGH 3,075,319

CONTINUOUS SANDBLAST APPARATUS Original Filed Jan. 5, 1960 3 Sheets-Sheet 2 IN VEN TOR.

Sylgeser H @6W/@M0 A TTRNE Y6 Jan. 29, 1963 s. H. BLUBAUGH CONTINUOUS sANDBLAsT APPARATUS original Filed Jan. 5., 1960 3 Sheets-Sheet 5 AMWX w EQRGQQ INVENTOR Syfwr H Blz/Zmayh ATTORNEYS @riginal application Jan.' 5,' 196i?, Ser, No: 607; DividedL andthis application Oct. 27, 196t),`er. No; 71,374l 10 ClaimS. (Cl. 5l-8) This invention relates to a continuous sandblas-t meth-h od and apparatus and more particularly to such method and apparatus as adapted tothe treatment ofconcrete paving surfaces.' The invention in its methodaspectis especially related to the finishing of concrete 'paving'surfac'e'sj for the purpose of preparingsuchsurface's for subsequent' painting operations and for the leveling of high or unevenportions of such surface. Y

In modern concrete paving operations, it has become customary to apply a sealing composition to thesurface of the fresh concrete to 'prevent the rapid-evaporation of moisture therefrom and to thus facilitate proper 'curing of the concrete. Such sealing compound mayfcomprisean organic solvent containing lacquer and` a relatively highproportion of wax-like constituents. Whenl applied to the concrete surface, it provides an effective sealing membrane. While such membrane is very effectivel in per'- forming the desired function of eliminatingf'r'apid evaporation of moisture, applicant has found thatvwhen paint is applied over such surface, particularly on highways, airstrips, parking lots, and other areas subject to heavy traffic, the life of the painted surfaceis relatively short.l Uny til the present invention, neitherl the cause o'fsuclishort` paint life nor the solution to this problem'hadbeen dis-f covered. I Applicant hasnow found thatI if the membrane left by the curing compound isremove'd as a preliminary step in the painting opera-tions, the life of the painteven# ually applied is substantially lengthened. Further, applicant has developed a method and apparatus'l whereby the sealing membrane not'only can be removedfin a rapidfand effective manner, butduring'the operation to remove such sealing membrane high or uneven spots may be removed from new concrete surfaces, thereby bringing them up to the rigid specifications imposed by federal andlstate high-V way and airport olhcials.

It is, therefore, a general objectvof the present inventiont'o provide a rapid andeconomical methodeand apparatusY` for the linishingv of concrete paving surfaces;

A Another object ofthe invention is to provide ay con-V tinuous method for removing a surface membrane from concrete paving structures.

Another object of theinvention is toprovidean improvement in themethod of--painting concrete surfaces.

Another object of the invention isto provide a continuoussandblas'ting apparatus forI surface treatment of concrete pavements.

A further object of the invention =is to provide' a'lsanjdblasting apparatus for removing the surfaceV layer' of a selected'strip 'on 'a concrete pavement'while'said apparatus isrcontinuusly' advancing in the directionof sucli'strip.

A still'further object of the'invention is to provide a continuous Sandblasting. apparatus' for travelingoverand treating the surface of a concrete'V pavement, 'Ywhereinall con-trois for driving vthe vehicle and'for' operating the sa'ridblasting equipmentare Within the reach of a'sin'gle' operator.

These and other objects andfadvantages' of the inverti tion will be more readily understood from the following description'taken'in conjunction with the attached'drawings, in which:

FIG. 1 is aplanview showing applicants no'velsand# blasting apparatus' inthe process ofpreparing a concrete highway surface for the' reception of an edge paint'strip;

niteri States Patent 3,075,319 Patented Jan. 29,1963

FIG. 2 is a side elevation of the novel Sandblasting ap` paratus shown in FIG. l;

FIG. 3 is afragmentary, sectional view taken onthet FIG. 8 is a diagrammatic view showing the valve of FIG. 7 in a different control position.

The invention is oneof its method aspects comprises an improvement in`V the painting of concrete surfaces v which have been seal-coated with a curing compound to provide a thin surface membrane retarding evaporation of moisture, such improvement including the step of sandblasting the concrete surface in a continuously moving pathsubstantially the widthV of the surface to be painted; to therebyremove the sealing membrane. The'method also involve'sa new'combination ofsteps for treating concrete pavements which have been seal-coated as described, including sandblasting-thesurface to be painted to there-'- byv removeV the membrane, acid-treating the sandblasted surface to kneutralize alkaline' substances", and applying paint? to the so-treated surface; The combination may also comprise the additionalstepof sandblastin'grhigh or uneven spots inthe concrete surface adjacent the'path'pre pared for painting to thereby provide a finished and painted pavement. It'w'ill be understood, howe'venthat the latter step has utility alone as well as in the combinar tion with the paintingope'ration.

Referring'A nowA to the` drawings', and particularly to FIGS. 1 andL 2, the apparatus is shown to comprise a truck generally designated as 10; having a chassis" 12 mounted on wheels'14 in'aconventional manner. At the forward end ofthe chassis' is a conventionaltruck-driving assembly, including' a cab 16 containing the usual contr'ols foroperatingr the'vehicle on ahighway. Thusgas shownin'FIG; l', the truck ltlmay bel drivenv downa section o`f concrete' highway pavement generally designated as 18', toprovide a treated edgesti'ip'19Q. Center'lines' and other marking lines can' be pre-treated'in'thesarne manner. v p

Mounted upon the' chassislZv to therear 'of tlie'l'c'ab r1'6 is" a' sand supply bin" 20 having a forwardly. sloping boti tom 2211 The bin may bevde'si'g'ne'd for any desiredy capacitybut preferably holds severalcubic yardsy of sand, i.e., suilcient sand for prolonged'supp'ly without'relling The' r sand supply bin 20' is supported onj chassisy 12 by means of channel-members 2'4 overlying the chassis `mem ber lzland` secured? thereto by means of lugsvv and-bolts 26'." The bottom" of the bin Ztl/rests upon inclinedchan nel members'fZS; which-aresupported by ve'r'ticalniembers tlwelded'to" the/channels 2.4'. The forward bottom end ofthe sand bin' 20' ab'uts the inside of an angle'- member 3 2, likewise welded't channel members Z4. Aga'sV tank`v 33 for supplyingfuel to-all engines ofthe apparatus is l-v cated iri the-space between-the'bottom 22 of the sand; supi ply binv 20 and the chassis 12 and'rests upon cross mein;v bers ofthe chassisV l2;

A pairpofair compressors 34:'aud 35 are mounted; on eitherV side of the sand binY 20 upon the channels 24 to which they are securedby anyl suitable means. The air compressors 34 and l3'6 are protected from the weather by any suitableA covering means 38.

TheV top of Ythe-sandA supply bin'Z/is'provided with' an opening having a cover 40 which is hinged at its rear end as at 42- andl is adapted tol be propped open by brace' member 44 during a lling operation. In order rapidly to ll the bin 20 with sand while the device is on the job, a moving belt conveyor 46 is mounted to extend above and forward of the cab 16. The top end of the belt conveyor 46 is supported by means of a shaft 48 journaled in a pair of brackets 50 secured to the top of bin 20. The shaft 48 is arranged to be driven by means of sprocket wheel 52, connected by chain drive 54 to a power take-off 56 from the truck transmission.

The forward end of the conveyor 46 is supported within a rectangular frame SS secured at its lower end to the forward portion of the chassis 12. The forward end of the conveyor 46 is vertically adjustable to a selected position within frame SS by rotation about the shaft 48 as an axis. Such adjustment is accomplished by means of a pulley 60, cable 62, and hand winch 64. The orward extremity of belt conveyor 46 may, therefore, be lowered to receive sand from a dump truck which backs into position ahead of the Sandblasting apparatus 101. `Suitable means (not shown) are provided for locking the conveyor in the seiected position. A hopper 66 at the lower end of the conveyor 46, as shown in FIG. 1, facilitates the sand-loading operation.

When the sandblast apparatus is to be moved at a rapid rate over the highway, as from one job to another, the sand conveyor 46 is moved to its topmost position land there secured so as not to obscure the vision of the driver of the vehicle. When the device 10 is in operation for sandblast purposes to provide a surface strip down the edge of a concrete pavement, as shown for example in FIG. 1, the conveyor 46 is secured in a lowered position whereby it may receive sand from a sand truck and, as will be described later, may also serve as a holder for a guide means 68 (FIG. 1), making it easier for the driver to properly position the sandblast nozzles with respect to the pavement as the vehicle advances in a forward direction.

Mounted beneath the forward compressor 34 and forward of the bottom of the sand supply bin 20, and just to the rear of the cab 16 are a pair of pressurized sand pots 70 and 72. The structure of these sand pots is best shown in FIGS. 3 and 4. Thus, each sand pot is connected by a conduit 74 to the bottom of the sand supply bin and is adapted to receive a supply of sand therefrom. A compressed air supply conduit or manifold 76 is mounted transversely beneath the truck chassis and receives compressed air from compressors 34 and 36 by means of supply conduits 7S and 80 (FIGS. 2 and 6). It will be understood that the apparatus is not limited to the use of two air compressors, the number of such compressors being governed by their output capacity. Thus, it is desirable to provide an air pressure of about 80 to 90 pounds per square inch or above and one or more compressors may be utilized for such purpose, depending upon their individual capacity.

Each of the pressurized sand pots 70 and 72 is connected at its bottom by means of a conduit S2 to the manifold 76 which at its outer end, as shown to the right of FIG. 3 and in FIG. 6, is provided with a bifurcated adaptor 84 for connection with a pair of high-pressure, rubber-lined, exible hoses 86. These hoses 86 are connected to a pair of vertically disposed, laterally spaced steel pipes 88 which, for example, may be about 8 inches long and -"/s inch inside diameter. The pipes 88, which provide nozzles for the Sandblasting equipment, are car-v ried by and extend through the top of a box 90 mounted for vertical adjustment with respect to an underlying concrete surface by means of a vertical standard 92 secured to the base of compressor 36 by means of bolts 94, as shown in FIG. 3. A plurality of bolt holes 96 are provided in the standard 92 so that a selected vertical position of the box 90 and pipes SS may be chosen.

The box 90, as shown, comprises rubber side walls 98 around three sides thereof, the side away from the truck being open to permit the escape of sand and air. It will numeral 100.

be understood, of course, that such box could be completely closed and other means for removing sand therefrom could be provided, such as vacuum means attached to a cyclone separator (not shown).

Referring now to the air-and-sand controls for the apparatus and with particular reference to FIG. 6, it will be noted that all of the controls are placed within reach of the truck operators position designated by reference Each of the pressurized sand pots 70 and 72 is provided with two valves for sand control, one, generally designated by reference numeral 102, in conduit 74 between the sand pot and the sand supply bin 20, and the other, generally designated by reference numeral 104, at the bottom of the sand pot for controlling the flow of sand from the pressurized sand pot to the manifold 76. These valves 102 and 104 are operated by mechanical linkages 106 and 108, respectively, shown in dotted lines in FIG. 6. The linkages 106 and 108, in

` turn, are connected to control levers 110 and 112 in the cab 16. Levers for the control of the valves 102 and 104 of the right sand pot 70 may be located tothe right of the operators position in the cab, and levers for the control of the left sand pot 72 may be mounted to the left of the operators position, as indicated.

The structure of the valves 102 and 104 for the pressurized sand pots 70 and 72 isillustrated in FIG. 4. Thus, the top valve 102 comprises a valve seat 114 positioned within the top of the sand pot itself. A rubber plunger member 116 is adapted to reciprocate within such seat 114 to open or close the valve. Four guide members 118 depending from the valve seat 114 facilitate the proper alignment of the plunger 116 during actuation. Actuation of the valve 102 is accomplished by means of the mechanical linkage 106, which includes a pivot 107 fixed to the truck chassis 12. By pushing the lever forward, as shown in FIG. 4, the linkage 106 will cause plunger 116 to be lowered from its seat 114, thereby opening the valve. The sand pot 70 thereby iills with sand by gravity flow from bin 20. It will be noted that the valve plunger 116 in its closed position, as shown in FIG. 4, will be maintained in such position by means of air pressure in the pressurized sand pot 70. Pressure in the sand pot 70 is released, as will presently be described, when the valve 102 is to be opened for the replenishing of sand from bin 20 and air pressure is restored while the valve is being closed, thereby facilitating its closure.

The lower valve 104, likewise, may include a valve seat 120 positioned within the sand pot 70 and a cooperating plunger 122 adapted for reciprocation therein. Guide members 121 maintain plunger 122 in proper alignment. The plunger 122 in the closed position of the valve is maintained in such position by the air pressure in manifold 76 during the lling of the said pot, and this valve is opened only when air pressure in the pot is equalized with that in the manifold 76. Valve 104 is actuated by mechanical linkage 108. By pulling lever 112 to the rear, as shown in FIG. 4, shaft 123, comprising a part of the linkage 108 and extending through the wall of the sand pot, is rotated to cause plunger 122 to be lowered.

The sand pots 70 and 72 are provided with pressureequalizing lines 124 and 126 connected at the top of the pressure pots as shown and leading to an air-valve control unit generally designated at (FIG. 6), also positioned in the cab in easy reach of the operator of the vehicle. Air pressure from the compressor line is provided to the air-valve control unit 130 by means of a branch conduit 132 leading to a four-way connector 134. A pressure gauge 136 is provided in the line 132 within the line of vision of the operator. A conduit 13S containing a cutoff valve 140 leads through a connector 142 to a vent 144 which exhausts to atmosphere. The pressure-equalizing lines 124 and 126 to the sand pots 70 and 72 are connected by means of valves 146 and 148, respectively, to connector 134 whereby these lines may receive air from branch line 132. The valves 146 and 148 are connected The valves'146 and 148 are constructedas shown FIGS.v 7 and 8, so that in one positionthereof, as shown in FIG.' 7, thejline pressure is connected to the pressure pot` to Yequalize the air pressure therein with that inmanifold 76; and in the other position, asl shown in FIG. 8, the line pressure is cut Voif'and the-pressure pot 'is ventedto the atmosphere. v

In the operation of the device, as for example, to prepare an edge strip along aconcrete highway pavement for the receptionof' paint, the apparatus 10 after having its'sand hopper'iilled with sand by means of conveyor 46 is positioned at the edge of the pavement, as shown in FIG. 1. Air compressors34 and 36V are then started',l valve Mtl-(FIG. 6') beingopened to the/atmosphere, andY valves 146 and 148 likewise being open to the'atrnosphere, as shown for example inFIG. 8, thereby, releasing any airV pressure from the sand" pots 70 and 72. AThe lower valve 1 0-4in each of the sandpots is in'closed position, as shown in FIG. 5. After the compressors are operating properly, valve 140 may be closed and the pressure will build up in the line by gauge 136. Eighty to ninety pounds of pressure have been found satisfactory, but greater pressures and increased forward speed y are contemplated. Valve 140 provides a'reaciyv means for regulating thev air pressure to a uniform value from the' cab, excessive pressure beingl reduced by slightlycracking thevalve'.

The ltop valves 102 between the sand bin 20 and 'pressure' pots are now opened bythe operator'by the manipulation of levers 11G-to permit the pressure pots toreceive a load of sand by gravity ow from the hopper'20. The bottom valves are maintainedin closed position by means of the line' pressure in manifold 76 beneath t h e plungers 122 of*Y valves 104. After the pressurepots 70'and 72'are filled, top valves 102 are closed by manipulation of'V hand levers 110 and,.if necessary, for easy closure of thesevalves, some compressed air may be' permitted to enter the pots 7@ and 72 by opening valves 146and 148 slightly towardY the positions shown'in FIG. 7 so that air pressure under the plunger 116will`fa`cilitate theclosing ofthe top valve 102.

AssumingY that it'is` desired t'o now' operate by use of sand from thepressure pot` 72,',the air-valve 148 (FIG. 6) is fully opened to the position shown inFIG. 7 'to permit the pressure tofully equalize in thepot 72 with the line pressure in manifold 76'. Leverl 112 is now operated to open the valve 104 by dropping the plunger 122 (FIG. 4) and sand will gravity feed intothe manifold 76' to be carried therethrough by therapidly moving air stream and through the downwardly directed pipes 8 8 at the end of the exiblel hoses 86; to therebyimpinge with great force upon the underlying-concrete surface.

The-pipes 88 whenset on 4 centers and havingf their vents positionedY about twofeet'from the concrete will clean the surface membrane from such concrete in about a 6" wide strip, shown at 19 (FIG. 1), while the truck is being advanced in a forward direction at a rate of about to 7 miles per hour. The nozzle spacing can be changed and additional nozzles may be added if wider strips are desired. Adjustment of the nozzles vertically with respect to the surface will also effect an adjustment of the width of the sandblast path. However, the nozzle ends are usually positioned at least 6" away from the surface of the pavement.

The operator of the truck may keep the vehicle in proper alignment by maintaining a line of sight against the edge of the highway across the tip of guide 68 (FIG. l) carried by the forward portion of the said conveyor 46. Further, due to the positioning of the nozzle box 90 below and adjacent the side of cab 16, it is possible for the driver to observe at all times whether or not the device is properly operating. Thus, one operator can drive to the desired extent, as indicated" the vehicleandicon'trol all of thesandblasting operations while sitting within the cab.

The device may be continuously' operated throughout the working' day tocover a great number ofmiles of treated pavement. A'so'n'e pressure pot is exhausted ofl sand, operation is" readily shifted to thev other pressure pot b y proper'rnanipulation of the valves and levers. Thus, assuming fthe sand pot`72 was the rst to be placed on the line, sand pot '7 0being illediin readiness for continued operation, uponjthe' exhaustion of sand from pot 72, the lower sand valve 104m` pot 70 is simply opened by manipulation of rightfhand lever 112. The Sandblasting operation continues with sand from this pot. Valve 146, of course, has been openedvto provide pressure equalization between thevsand-filled pot 70 and the line 76. As soon as this switch-over has been accomplished, the ope'rator Vpushes the left-hand lever 112 to close lower valve 1t4in1the pot 72, turns valve 148 to vent this pot to the atmosphere'and then opens valve 102 between the pot and the sand-bin 20to permit pot 72 to gravity ll. When itis lled, he closes valve 102, switches the valve 148 to pressure-equalize this pot' with the line, and is thus in readiness'for placingthis potinto operation` as soon as the other isemptied.

AsT soon as the surface membrane is removed, the strip maybe acid-treatedV to neutralize* alkalies and painted in the usualv nianner; It is'thought that removal of the membranepermits the desired action of the acid to take place so -that the paint is not killed by'the action of the alkalies whieheventually come through such membrane. However, applicant does notV wish to be bound by such theory, Suffice tosay' that the life of the paint is substantially prolonged by reason of the preliminary step.

In' modern construction, after. anew co-ncrete paving operation, inspectors determine the existence of high spots or uneven' spots inthe surface. These spots are usually marked' withT a' daub of paint of characteristic color. Heretofore,the1paving contractors have util-ized a special piece of. grinding equipment comprising a series of rotating` knivesoperated by ai gasoline motor for grinding downfthesehigh oruneven` spots. Such grinding may take as muchas 10'or l5 minutes for a spot of several feetin diameter, andi the grinding knives must soon be It is a tedious,V time-consuming, and costly operation. v

In accordancel with the present'method andl apparatus for riishing concrete paving'surfaces; an auxiliary, flexible air hose. (not shown) is provided, having a nozzle at the endthereof; This Vauxiliary hosegcan be coupled to ma'nifold-76 after rs't uncoupling'the hoses 86 attached to-the sandblast'box 90; Hoses'86 are simply coiled out-.of the way and aftei the auxiliary hose has been attached, the other outlet of the member 84 is closed by meansV of a threaded plug. Sandblasting of the high or uneven spotsin the paving surface is accomplished through such' auxiliary hose. It has been found that a high spot requiring as much as l0 or 15 minutes by the convention-al grinding equipment can be removed within a matter of seconds by means of the present equipment. It will be seen that a great deal of time and effort have been saved by the use of the present device as a replacement for such grinding equipment.

When the device is used for preparing strips on a concrete surface for reception of paint, high spots can be removed from .such surface at the same time by simply stopping -the vehicle as each marked high spot is reached, attaching the auxiliary hose, removing the high spot without moving the vehicle out of alignment with the strip to be prepared, and then shifting back to normal operation along the original path. However, the device may be used solely for the purpose of removing high spots from pavement without regard to painting operation. Both procedures are facilitated by the possibility of prolonged continuous operation, easy control, and rapid transportability 4from place to place.

If it is desired to cut down upon dust, a water tank may be mounted on the truck chassis at an appropriate location and water therefrom dropped on the paved surface Ahnmediately ahead of the sandblast nozzles at a rate of approximately gallons per mile.

It will be apparent to those skilled in the art that a great number of modifications are po-ssible in the method and apparatus without departing from the spirit and scope of the invention as set forth in the appended claims.

This lapplication is a division of my copending application Serial No. 607, tiled January 5, 1960.

I claim:

l. Portable Sandblasting apparatus for continuous treatment of pavement surfaces, comprising: a motor-driven vehicle having a cab and drivers position at the forward end thereof, a sand supply bin mounted on the vehicle chassis, an air compressor, 'a pair of pressurized sand chambers positioned below said sand supply bin and adapted to receive sand therefrom, a sandblast nozzle mounted on said vehicle on one side of said cab and within the visual observation of said driver, a conduit connecting said air compressor to said nozzle, conduit means connecting said pressurized sand chambers to said conduit to provide a iiow of sand thereto, and control means including means in said cab within reach of said drivers position for selectively controlling the air supply from said compressor to said pressure chambers, selectively controlling the supply of sand from said sand bin to said pressurized chambers, and selectively controlling `the flow lof sand from said chambers into said conduit so that one of said chambers may be used while the other is being filled with sand to thereby provide a continuous supply o-f sand to said conduit for a Sandblasting operation.

2. The apparatus of claim 1 wherein said vehicle is provided with a power-driven sand conveyor for filling said supply bin from a supply truck.

3. The apparatus of claim 2 wherein said sand conveyor is mounted above the cab of said vehicle and extends forward thereof and wherein means are provided for raising the forward end of said conveyor between operations to enable the vehicle to be driven from one job to another without obscuring the Vision of the driver.

4. The apparatus of claim 3 wherein guide means are positioned on the forward end of said conveyor in line of sight for the drivers position for facilitating alignment of `the vehicle by the driver along a selected path.

5. In a portable ySandblasting apparatus having conduit means connecting a sandblast nozzle with a source of compressed air and with a source of sand, Ithe improvement comprising `a pair of pressurizable sand chambers having their lower ends connected to said conduit means for the discharge of sand thereto, a relatively large sand supply bin positioned above said sand chambers and connected to the upper ends of said chambers to supply sand to said chambers, means for selectively connecting each of said sand chambers to said source of compressed air and to ythe atmosphere, means for selectively controlling the sand supply from said supply bin to said sand chambers, and means for selectively controlling the discharge of sand from said sand chambers to said conduit means, whereby one of said sand chambers may discharge sand into said conduit means while the other sand chamber is being filled with sand from said supply bin to thereby provide a continuous supply of sand lto said conduit means and nozzle.

6. In a portable Sandblasting apparatus having conduit means connecting a sandblast nozzle with a source of `compressed air and with a source of sand, the improvement comprising: a pair of sand chambers having their lower ends connected to said conduit means to supply sand thereto, each of Said sand chambers having a discharge valve at the lower end thereof, a relatively large sand supply bin positioned above said sand chambers, means connecting said supply bin to each of said sand chambers for gravity feed of sand thereto from said bin, said connecting means including inlet valves for each of said sand chambers, means connecting said sand chambersto said source of compressed air for equalizing the pressure `in said chambers with that in said conduit, said latter connecting means including 4control means for selectively pressurizing and venting said chambers to the atmosphere, whereby one of said chambers while pressurized may feed sand into said conduit means while the other of said chambers while vented to atmosphere is being iilled from said supply bin thereby to provide for a continuous sand supply to said nozzle.

7. The apparatus as defined in claim 6 wherein said discharge valves are arranged to be urged toward a closed position by pressure dilferential between said sand chamber and said conduit means when said chamber is vented to the atmosphere.

8. The apparatus as defined in claim 6 wherein said inlet valves are arranged to be urged toward a closed position by pressure differential between said sand sup-ply bin and said sand chambers when the latter are pressurlzed.

, 9. T he .apparatus as delined in claim 6 wherein means for remotely actuating said inlet and discharge valves are provided and said actuating means and the control means for selectively pressurizing and venting said sand chambers are positioned within the reach of a single operator. 10. The apparatus as defined in claim 9 including a motor-driven vehicle carrying said Sandblasting equipment, said vehicle including a cab for a driver, and said valve-actuating means and c-ontrol means being positioned within said cab within reach of the drivers position.

References Cited in the le of this patent UNITED STATES PATENTS 

1. PORTABLE SANDBLASTING APPARATUS FOR CONTINUOUS TREATMENT OF PAVEMENT SURFACES, COMPRISING: A MOTOR-DRIVEN VEHICLE HAVING A CAB AND DRIVER''S POSITION AT THE FORWARD END THEREOF, A SAND SUPPLY BIN MOUNTED ON THE VEHICLE CHASSIS, AN AIR COMPRESSOR, A PAIR OF PRESSURIZED SAND CHAMBERS POSITIONED BELOW SAID SAND SUPPLY BIN AND ADAPTED TO RECEIVE SAND THEREFROM, A SANDBLAST NOZZLE MOUNTED ON SAID VEHICLE ON ONE SIDE OF SAID CAB AND WITHIN THE VISUAL OBSERVATION OF SAID DRIVER, A CONDUIT CONNECTING SAID AIR COMPRESSOR TO SAID NOZZLE, CONDUIT MEANS CONNECTING SAID PRESSURIZED SAND CHAMBERS TO SAID CONDUIT TO PROVIDE A FLOW OF SAND THERETO, AND CONTROL MEANS INCLUDING MEANS IN SAID CAB WITHIN REACH OF SAID DRIVER''S POSITION FOR SELECTIVELY CONTROLLING THE AIR SUPPLY FROM SAID COMPRESSOR TO SAID PRESSURE CHAMBERS, SELECTIVELY CONTROLLING THE SUPPLY OF SAND FROM SAID SAND BIN TO SAID PRESSURIZED CHAMBERS, AND SELECTIVELY CONTROLLING THE FLOW OF SAND FROM SAID CHAMBERS INTO SAID CONDUIT SO THAT ONE OF SAID CHAMBERS MAY BE USED WHILE THE OTHER IS BEING FILLED WITH SAND TO THEREBY PROVIDE A CONTINUOUS SUPPLY OF SAND TO SAID CONDUIT FOR A SANDBLASTING OPERATION. 